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</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../language.html" title="cpp/language">C++ 语言</a></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="expressions.html" title="cpp/language/expressions"> 表达式</a><div class="t-navbar-menu"><div><div style="display:inline-block">
<div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv-h2"><td colspan="5"> 概述 </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="value_category.html" title="cpp/language/value category"> 值类别</a>（左值 lvalue、右值 rvalue、亡值 xvalue）</td></tr>
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<tr class="t-nv"><td colspan="5"> <a href="constant_expression.html" title="cpp/language/constant expression"> 常量表达式</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="expressions.html#.E4.B8.8D.E6.B1.82.E5.80.BC.E8.A1.A8.E8.BE.BE.E5.BC.8F" title="cpp/language/expressions"> 不求值表达式</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="expressions.html#.E5.88.9D.E7.AD.89.E8.A1.A8.E8.BE.BE.E5.BC.8F" title="cpp/language/expressions"> 初等表达式</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="lambda.html" title="cpp/language/lambda">lambda 表达式</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv-h2"><td colspan="5"> 字面量 </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="integer_literal.html" title="cpp/language/integer literal">整数字面量</a></td></tr>
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<tr class="t-nv"><td colspan="5"> <a href="character_literal.html" title="cpp/language/character literal">字符字面量</a>，包含<a href="escape.html" title="cpp/language/escape">转义序列</a></td></tr>
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<tr class="t-nv"><td colspan="5"> <a href="nullptr.html" title="cpp/language/nullptr">空指针字面量</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
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<tr class="t-nv-h2"><td colspan="5"> 运算符 </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_assignment.html" title="cpp/language/operator assignment"> 赋值运算符</a>:
<code>a=b</code>, <code>a+=b</code>, <code>a-=b</code>, <code>a*=b</code>, <code>a/=b</code>, <code>a%=b</code>, <code>a&amp;=b</code>, <code>a|=b</code>, <code>a^=b</code>, <code>a&lt;&lt;=b</code>, <code>a&gt;&gt;=b</code></td></tr>
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<code>+a</code>, <code>-a</code>, <code>a+b</code>, <code>a-b</code>, <code>a*b</code>, <code>a/b</code>, <code>a%b</code>, <code>~a</code>, <code>a&amp;b</code>, <code>a|b</code>, <code>a^b</code>, <code>a&lt;&lt;b</code>, <code>a&gt;&gt;b</code> </td></tr>
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<tr class="t-nv"><td colspan="5"> <a href="operator_comparison.html" title="cpp/language/operator comparison"> 比较运算符</a>: <code>a==b</code>, <code>a!=b</code>, <code>a&lt;b</code>, <code>a&gt;b</code>, <code>a&lt;=b</code>, <code>a&gt;=b</code>, <code>a&lt;=&gt;b</code><span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_member_access.html" title="cpp/language/operator member access"> 成员访问运算符</a>: <code>a[b]</code>, <code>*a</code>, <code>&amp;a</code>, <code>a-&gt;b</code>, <code>a.b</code>, <code>a-&gt;*b</code>, <code>a.*b</code></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_other.html" title="cpp/language/operator other"> 其他运算符</a>: <code>a(...)</code>, <code>a,b</code>, <code>a?b:c</code> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="default_comparisons.html" title="cpp/language/default comparisons">默认比较</a><span class="t-mark-rev t-since-cxx20">(C++20)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_alternative.html" title="cpp/language/operator alternative">运算符的代用表示</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operator_precedence.html" title="cpp/language/operator precedence">优先级和结合性</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="fold.html" title="cpp/language/fold">折叠表达式</a><span class="t-mark-rev t-since-cxx17">(C++17)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="new.html" title="cpp/language/new">new 表达式</a></td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink">delete 表达式</strong></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="throw.html" title="cpp/language/throw">throw 表达式</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="alignof.html" title="cpp/language/alignof">alignof</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="sizeof.html" title="cpp/language/sizeof">sizeof</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="sizeof....html" title="cpp/language/sizeof...">sizeof...</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="typeid.html" title="cpp/language/typeid">typeid</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="noexcept.html" title="cpp/language/noexcept">noexcept</a><span class="t-mark-rev t-since-cxx11">(C++11)</span></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="operators.html" title="cpp/language/operators">运算符重载</a></td></tr>
<tr class="t-nv-h2"><td colspan="5"> 类型转换 </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="implicit_cast.html" title="cpp/language/implicit conversion">隐式转换</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="const_cast.html" title="cpp/language/const cast">const_cast</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="static_cast.html" title="cpp/language/static cast">static_cast</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="reinterpret_cast.html" title="cpp/language/reinterpret cast">reinterpret_cast</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="dynamic_cast.html" title="cpp/language/dynamic cast">dynamic_cast</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="explicit_cast.html" title="cpp/language/explicit cast">显式转换</a> <code>(T)a</code>, <code>T(a)</code></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="cast_operator.html" title="cpp/language/cast operator">用户定义转换</a></td></tr>
</table></div>
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<p>销毁先前由 <a href="new.html" title="cpp/language/new">new 表达式</a>分配的对象，并释放获得的内存区域
</p>
<h3><span class="mw-headline" id=".E8.AF.AD.E6.B3.95">语法</span></h3>
<table class="t-sdsc-begin">

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</td></tr>
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<td> <code><b>::</b></code><span class="t-mark">(可选)</span>    <code><b>delete   </b></code> <span class="t-spar">表达式</span>
</td>
<td> (1)
</td>
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</td></tr>



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</td></tr>
<tr class="t-sdsc">
<td> <code><b>::</b></code><span class="t-mark">(可选)</span>    <code><b>delete []</b></code> <span class="t-spar">表达式</span>
</td>
<td> (2)
</td>
<td class="t-sdsc-nopad">
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<div class="t-li1"><span class="t-li">1)</span> 销毁 <a href="new.html" title="cpp/language/new">new 表达式</a>创建的单个非数组对象</div>
<div class="t-li1"><span class="t-li">2)</span> 销毁 <a href="new.html" title="cpp/language/new">new[] 表达式</a>创建的数组</div>
<h3><span class="mw-headline" id=".E8.A7.A3.E9.87.8A">解释</span></h3>
<p>对于第一种（非数组）形式，<span class="t-spar">表达式</span> 必须是指向对象类型的指针或可<a href="implicit_cast.html" title="cpp/language/implicit conversion">按语境隐式转换</a>到这种指针的类类型，且其值必须为<i>空 (null)</i> 或指向 <a href="new.html" title="cpp/language/new">new 表达式</a>所创建的非数组对象的指针，或指向 <a href="new.html" title="cpp/language/new">new 表达式</a>所创建的对象的基类子对象的指针。若 <span class="t-spar">表达式</span> 为其他值，包括它是通过<a href="new.html" title="cpp/language/new">new 表达式</a>的数组形式获得的指针的情况，其行为<a href="ub.html" title="cpp/language/ub">未定义</a>。
</p><p>对于第二种（数组）形式，<span class="t-spar">表达式</span> 必须是空指针值或先前由 <a href="new.html" title="cpp/language/new">new 表达式</a>的数组形式所获得的指针值。若 <span class="t-spar">表达式</span> 为其他值，包括若它是由 <a href="new.html" title="cpp/language/new">new 表达式</a>的非数组形式获得的指针的情况，其行为<a href="ub.html" title="cpp/language/ub">未定义</a>。
</p><p>表达式的结果始终具有 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span> 类型。
</p><p>若被删除的对象在删除点拥有不完整类类型，且完整类类型拥有非平凡析构函数或解分配函数，则行为未定义。
</p><p>若 <span class="t-spar">表达式</span> 不是空指针<span class="t-rev-inl t-since-cxx20"><span>且<a href="../memory/new/operator_delete.html" title="cpp/memory/new/operator delete">解分配函数</a>不是销毁 delete</span> <span><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></span></span>，则 <code>delete</code> 表达式对被销毁的对象，或对要被销毁的数组的每个元素（从数组的最后元素行进到首元素），调用其<a href="destructor.html" title="cpp/language/destructor">析构函数</a>（若它存在）。
</p><p>然后，<span class="t-rev-inl t-since-cxx14"><span>除非其所匹配的 new 表达式已经与另一 new 表达式合并，否则</span> <span><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></span></span>无论析构函数是否抛出异常，delete 表达式都调用<a href="../memory/new/operator_delete.html" title="cpp/memory/new/operator delete">解分配函数</a>：<span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="../memory/new/operator_delete.html"><span class="kw689">operator delete</span></a></span></span>（对于表达式的第一种版本）或 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="../memory/new/operator_delete.html"><span class="kw689">operator delete</span></a><span class="br0">[</span><span class="br0">]</span></span></span>（对于表达式的第二种版本）。
</p><p>在 <span class="t-spar">表达式</span> 所指向对象的动态类型的作用域中<a href="lookup.html" title="cpp/language/lookup">查找</a>解分配函数的名字，这表示如果存在类特有解分配函数，则它将在全局版本之前被找到。若 <code>delete</code> 表达式中存在 <code><b>::</b></code>，则查找中只检查全局命名空间。
</p><p>若查找找到了多于一个解分配函数，按以下方式选择所调用的函数（有关这些函数及其效果的更详细描述见<a href="../memory/new/operator_delete.html" title="cpp/memory/new/operator delete">解分配函数</a>）：
</p>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx20"><td>
<ul><li> 若至少一个解分配函数为销毁 delete，则忽略所有非销毁 delete。
</li></ul>
</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td></tr>
<tr class="t-rev t-since-cxx17"><td>
<ul><li> 若类型的对齐要求超出 <code>__STDCPP_DEFAULT_NEW_ALIGNMENT__</code>，则优先采用具对齐解分配函数（有一个 <span class="t-lc"><a href="../memory/new/align_val_t.html" title="cpp/memory/new/align val t">std::align_val_t</a></span> 类型的形参）。对于其他类型，优先采用不具对齐解分配函数（没有 <span class="t-lc"><a href="../memory/new/align_val_t.html" title="cpp/memory/new/align val t">std::align_val_t</a></span> 类型的形参）。
</li></ul>
<dl><dd><ul><li> 若找到多于一个优先函数，则下一步中只考虑优先函数。
</li><li> 若找不到优先函数，则下一步中考虑非优先函数。
</li></ul>
</dd></dl>
<ul><li> 若只剩下一个函数，则选择该函数。
</li></ul>
</td>
<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td></tr>
</table>
<ul><li> 若找到的解分配函数是类特有的，则优先采用不具大小的类特有解分配函数（无 <span class="t-lc"><a href="../types/size_t.html" title="cpp/types/size t">std::size_t</a></span> 类型的形参）而不是具大小的类特有解分配函数（带 <span class="t-lc"><a href="../types/size_t.html" title="cpp/types/size t">std::size_t</a></span> 类型的形参）
</li></ul>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx14"><td>
<ul><li> 否则，查找抵达全局作用域，且：
</li></ul>
<dl><dd><ul><li> 若类型完整，且只对于 delete[]，若其操作数是指向拥有非平凡析构函数的类或其（可以多维）数组的指针，则选择具大小的全局函数（带 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="../types/size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a></span></span> 类型的形参）
</li><li> 否则，选择全局具大小解分配函数（带 std::size_t 类型的形参）还是全局不具大小解分配函数（无 std::size_t 类型的形参）是未指明的。
</li></ul>
</dd></dl>
</td>
<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td></tr>
</table>
<p>指向要被回收的存储块的指针会作为首个实参，传递给按上述方式所选择的<a href="../memory/new/operator_delete.html" title="cpp/memory/new/operator delete">解分配函数</a>。块大小作为可选的 <code>std::size_t</code> 实参传递。<span class="t-rev-inl t-since-cxx17"><span>对齐要求作为可选的 <code>std::align_val_t</code> 实参传递。</span> <span><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></span></span>
</p>
 <table class="t-rev-begin">
<tr class="t-rev t-until-cxx14"><td>
<p>若 <span class="t-spar">表达式</span> 求值为空指针值，则不调用析构函数，且可能也可能不调用解分配函数（这是实现定义的），但缺省的解分配函数保证在处理空指针时不做任何事。
</p>
</td>
<td><span class="t-mark-rev t-until-cxx14">(C++14 前)</span></td></tr>
<tr class="t-rev t-since-cxx14"><td>
<p>若 <span class="t-spar">表达式</span> 求值为空指针值，则不调用析构函数，且不调用解分配函数。
</p>
</td>
<td><span class="t-mark-rev t-since-cxx14">(C++14 起)</span></td></tr>
</table>
<p>若 <span class="t-spar">表达式</span> 求值为指向 <a href="new.html" title="cpp/language/new">new</a> 所分配的对象的基类子对象的指针，则基类的析构函数必须为虚，否则行为未定义。
</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
<p>不能删除指向 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span></span></span> 的指针，因为它不是指向完整对象类型的指针。
</p>
 <table class="t-rev-begin">
<tr class="t-rev t-since-cxx11"><td>
<p>因为关键词 <code>delete</code> 之后的一对方括号始终被解释为 delete 的数组形式，所以紧跟在 <code>delete</code> 之后的拥有空俘获列表的 lambda 表达式必须以括号括起来。
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="co1">// delete []{return new int; }(); // 解析错误</span>
delete <span class="br0">(</span><span class="br0">[</span><span class="br0">]</span><span class="br0">{</span><span class="kw1">return</span> new <span class="kw4">int</span><span class="sy4">;</span> <span class="br0">}</span><span class="br0">)</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// OK</span></pre></div></div>
</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td></tr>
</table>
<h3><span class="mw-headline" id=".E5.85.B3.E9.94.AE.E8.AF.8D">关键词</span></h3>
<p><a href="../keyword/delete.html" title="cpp/keyword/delete"><tt>delete</tt></a>
</p>
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